Leaving fullscreen causes tabs to have an empty space

I use my browser maximized, I just installed Opera for the first time and decided to use it as my main browser, but discovered an annoying issue.

Every time I switch a video (or the browser itself with F11) to fullscreen and then switch back, there appears an empty bar above tabs, I have to click another tab in order to make it go away. At first I thought it caused my browser to go windowed, but that wasn't the case, here is a screenshot of what it looks like: